I had MANY MANY sleepovers as a child and have very fond memories with friends and I'm still friends with most of the girls I grew up with. I am a plane ticket away from everyone but we still stay in touch via email, text, facebook.
My daughter 18, participated in many sleepovers from about age 5 and up. She too has many fond memories. As she got older, say starting middle school age through high school, there were girls at my house every night of the weekend sleeping over. I have no issues with sleepovers. Most of the time, girls slept over at our house because my daughter had the run of the entire upstairs, everyone had a bed, no siblings to deal with and I liked knowing what was going on. I enjoyed having the safe place for girls to come sleep over.
Daughter slept over at other friends homes often as well as she grew up. She learned a lot about families with other children and the dynamics of other families as well. I think that is a good thing.
I don't understand a "no sleepover" rule and the fear some parents have because of it but if that is how it works for their family, I respect that.
I think there could certainly be some balance involved instead of being so over protective that a child does not get to participate in something that is fun and helps them build relationships.
There are also parents to will say no to sleepovers because they don't want to bother with having children at their house.
I never looked for a tit for tat on sleepovers, etc. I just wanted my daughter to have as full of a childhood as possible. I have been very open minded, kept communication wide open and I have not been one to hover over everything she does. You can't keep children wrapped in bubble wrap and expect them to come out at 18 knowing all the basics, social graces and have relationships with people outside the family dynamic.
So yes, you could say I am pro sleepover, daughter started around 5 and we hardly ever had an issue with sleepovers.